湖北蛇屋山红土型金矿床PSDs特征及其意义

PSDs characteristics and its significance of Shewushan lateritic gold ore deposit,Hubei province

土壤颗粒粒度分布(PSDs)是复杂物理化学作用的结果,研究表明,分形理论是刻画这一复杂过程的有利工具。通过对蛇屋山金矿床赋矿红土的PSDs研究发现,赋矿红土颗粒平均粒度在3.42～28.53μm之间,同时从风化壳浅部到深部有增加的趋势。分形统计学研究表明,赋矿红土PSDs在1.71～9.46μm范围内具有分形特征(R2>0.94),分维值(D)变化范围为2.86～2.22。红土剖面样品的矿物组成、伊利石结晶度Kübler指数以及样品颗粒粒级的综合分析认为,随着Kübler指数不断增加,流体-土壤作用增强,黄铁矿的氧化、长石的黏土化等导致土壤颗粒由粉粒向黏粒的转化。D值与黏粒/粉粒含量的良好相关性指示了流体-土壤相互作用而导致红土颗粒的细粒化这一过程,具有一定的普适性。因此,颗粒粒度分形特征可以作为评价红土型风化成土过程的重要指标。

Previous studies showed that particle-size distributions（PSDs） of soil were resulted from complex physical-chemical processes and could be efficiently described by fractal theory.According to the research on PSDs of the ore-hosting laterite of Shewushan gold deposit,we found that the average particle sizes of the laterite are varied from 3.42 to 28.53 μm and the values increase as the altitude decreases.Fractal statistics studies showed that the ore-hosting laterite has the fractal characteristics ranging between 1.71 and 9.46 μm（R20.94） and the fractal dimensions（D） change from 2.22 to 2.86.Moreover,the mineral composition,Kübler index of illite crystallinity and particle size fraction data suggested that as the increasing of the Kübler index,fluid-soil reaction becomes strong and the oxidation of pyrite and the argillization of feldspar may result in the transformation from the silt to clay.The fine correlations between the D values and caly/silt indicated that the processes of fluid-soil interaction which caused the particle size reduction of the ore-hosting laterite might be very common during the lateritic weathering.Therefore,the fractal characteristics of PSDs can be an effective indicator to evaluate the processes of weathering and laterite formation.